Well operation for recovering oil from produced sand

ABSTRACT

In a well operating process for treating a mixture of water, unadsorbed gas and/or liquid hydrocarbons, and oily sand, after removing the unadsorbed hydrocarbons, the sand is de-oiled by repeatedly entraining it in streams of relatively high speed jets of water, centrifically separating an overflow of oily water and an underflow of sandy water in which the sand is substantially oil-free, and removing the oil from the overflow to leave a water which is substantially oil-free.

United States Patent 1191 Darley et al.

[ Oct. 9, 1973 WELL OPERATION FOR RECOVERING OIL FROM PRODUCED SAND [75] Inventors: Henry C. H. Darley, Houston, Tex.;

Morris C. Place, Jr., New Orleans,

I73 I Assignee: Shell Oil Company, Houston, Tex.

221 Filed: A r; 27, 1972 [2!] Appl. No.: 248.073

[52] 0.5. CI. 210/73, 2l0/84, 210/512 M [51] int. Cl B01d 21/26 [58] Field of Search 210/70, 73, 84, 195,

[56] References Cited UNITED STATES PATENTS 2,381,760 8/1945 Latham, Jr 210/84 X PRODUCED FL U/D CONTAINING WATER, mmgifi fi lv AND HYDROCARQO SAND SEPARATOR WATER AND 0111 SAND 2,154,968 7/1956 Uegteretal. ..2l0/5l2M 3,707,464 12/1972 Bohnset 3,716,480 2/1973 Finley et a1. 210/73 X Primary Examiner- John Adee Attorney-Harold L. Denkler et a1.

[57] ABSTRACT in a well operating process for treating a mixture of water, unadsorbed gas and/or liquid hydrocarbons, and oily sand, after removing the unadsorbed hydrocarbons, the sand is de-oiled by repeatedly entraining it in streams of relatively high speed jets of water, centrifically separating an overflow of oily water and an underflow of sandy water in which the sand is substantially oil-free, and removing the oil from the overflow to leave a water which is substantially oil-free.

7 Claims, 1 Drawing Figure OILY WATER OIL a FLOTAT/ON CELL -----cLEA/v WATER CLEAN WATER 1 RE C YCLE DE-O/LED SAND WELL OPERATION FOR RECOVERING OIL FROM PRODUCED SAND BACKGROUND OF THE INVENTION This invention relates to a well operating process for treating fluid produced from a sand productive hydro carbon recovery well in order to isolate marketable hydrocarbons, a substantially oil-free water and a substantially oil-free sand. The invention is particularly useful for operating wells in an ecologically sensitive environment such as an offshore, coastal or marshland environment. In numerous conventionalwell operating processes, fluids containing water, unadsorbed hydrocarbons and oily sand (containing adsorbed hydrocarbons) are treated to isolate substantially only the unadsorbed hydrocarbons while leaving a residue that is apt tocontain oily water and/or oily sand which might be damaging to the ecology. Alternatively, relatively expensive treatments have been proposedifor de-oiling such a sand; for example, by removing the unadsorbed hydrocarbons and a portion of the water and then carbonizing the oil on the oily sandby contacting a residual water. slurry of it with a hot gas, in the manner described in US. Pat. No. 3,516,490;

SUMMARY os THE INVENTION The invention relatesto treating a mixture of water, unadsorbed hydrocarbons, and oily sand to isolate the hydrocarbons, a substantially oil-free water and a substantially oil-free sand. This is accomplished by removing the unadsorbed hydrocarbons, partially de-oiling sand by entraining itin a stream of relatively high speed jOtOfjWfitEl', centrifugally separating the resultant sandladenwater stream by. removing an oily water overflow.

DESCRIPTION OF THE DRAWING.

The drawing is a schematic illustration of apparatus suitable for. use in the. present invention.

DESCRIPTION OF THE INVENTION The invention involves a combination of steps which can be conducted by means of techniques andequipment that are individually currently available to those skilled in the art. In using the present invention, one or a plurality of wells can be operated simultaneouslyor sequentially. Thefluids produced from a group. of wells are preferably conveyed to a common apparatus for simultaneously treating a mixture of the fluids.

In using an apparatus of the type shown in the drawing, a produced fluid containingflwater, unadsorbed hydrocarbons and oily sand is treated in hydrocarbon separator l to remove the gaseous and/or oil phase hydrocarbons that are not adsorbed on the oily sand. Such a hydrocarbon removal can utilize currently available equipment and techniques, such as gravity segregation, hydrocarbon volatilization, emulsion breaking, and the like. The removal of the unadsorbed hydrocarbons leaves a water suspension of oily sand grains.

Where desirable, the sand de-oiling steps of the present invention can. be enhanced by contacting the water suspension of oily sand grains with .an effective amount of a surfactant for increasing the surface tension of an oil-phase liquid. A particularly suitable surfactant material of this type comprises a polar-group-containing aliphatic solvent solution of a relatively long chain aliphatic alcohol, ie an Oil Herder" surfactant, described in more detail in patent application Ser. No. 15,952, filed Mar. 2, 1970, the disclosures of which are incorporated herein by reference.

The sand in the suspension of water and oily sand is partially deoiled by entraining the suspension in the stream of a relatively high speed jet of waterin the Venturi arrangement 2. Such a Venturi arrangement can comprise an eductor, or jet pump, type of apparatus. In the illustrated jet-cyclone type of device, water is forced through nozzle 3 to form a relatively high speed jet of water within a relatively large diameter conduit 4. The slurry of oily sand and water inflows through conduit 5 into conduit 4 where it is entrained in the jet stream. The resultant sand-laden stream of water is separated in the cyclone type of centrifugal device 7. The present centrifugal separating means can advantageously be a conventional cyclone type ofdevice inwhich the centrifugal force is generated by the rapidswirling motion of the entering stream of water. The centrifugation removes an underflow stream of sandy water containing at least partially de-oiled sand and an overflow stream of oily water-containing oil released-from the sand. 7

The present inventionis, at least in part, premisedon a discovery that entraining a water suspension of oily sand in the stream of the relatively high speed jet of water and substantially immediately centrifugally removing a.water suspension of at least partiallyde-oiled sand while leaving an oily water is; a uniquely efficient way of removing and isolating the oil that wasadsorbed on the sand. As a slurry of sandgrains is entrained in a stream of water the grain surfaces are subjected to a strong shearing action during the time the waterin the stream moves along the grain surfaces until the grains have been accelerated (by the friction of the shearing action) to substantially the speed of the waterstream; By immediately centrifuging the sand laden stream, the oily water thatis left by the centrifugal removal of the heavier sand grains is substantially immediately removed from :the area of agitation so that the oil tends to remain in relatively large droplets rather than being sheared down to a coloidal size.

The sandy underflow containing partially. de-oiled sand is treated in the same way in at least one additional Venturi jet device 2a and centrifugal separating device 71: to subsequently form'a sandy water underflow that contains a substantially oil-free sand. As will be apparent to those skilled in the art, the Venturi jet arrangements 2 andZaand centrifugal separating devices 7 and 7a can be separated by conduits, chambers, or the like, as long as substantially all of the partially dc-oiled sand in the underflow from the centrifugal device 7 is maintained in suspension or is re-entrained to form a sand slurry that is flowed into contact with the relatively high spaced jet of water in at least one additional jet device 211. For example, a bank of parallel jet cyclones (e.g. combination of the Venturi jet arrange ments 2 and the centrifugal devices 7) can discharge their underflows containing partially de-oiled sand into one or more chambers from which the sand is reentrained in water if necessary and is then transported into the jet streams of a second bank of jet-cyclones.

The oily water overflow from each such sand grain de-oiling stage is flowed into flotation cell 8 in which the oil is removed while leaving a clean water that is substantially oil-free. At least a portion of that clean water is preferably supplied to pump 9 which drives it through the jet nozzles 3 and 3a of the Venturi devices to provide relatively high speed jets of water. I

In general, the flotation cell 8 can be replaced by one or more of a variety of oil-water-separators for removing the oil from an oily water. Such devices can include one or more flotation coalescing, oil-sorbing, gravity seggregating, filtering, or the like, elements in various combinations, as long as such devices are adapted to remove substantially all of the oil from an oily-water.

As known to those skilled in the art, the sand in a produced fluid containing water, hydrocarbons and oily sand is apt to be contaminated with clay. The recovery disperse the clay within the water. As soon as such an agitation ceases, the clay forms flocs comprising chains and complexes with the oil droplets and these grow to become relatively large flocs that tend to sediment or settle out of the suspension.

In research leading to the present invention, it was found that the amount of such flocs that are formed and the time for them to appear is dependent upon: (1) the degree of agitation of a slurry of the sand and water, the more violent the agitation, the quicker the flocs are formed; (2) the length of time agitated, prolonged agitation causing voluminous flocs to form and (3) the concentration of the sand in the slurry. With a 1 percent by weight sand-in-water slurry, a one minute agitation in a Waring Blender causes visible flocs to appear soon after about 1 hour. When the concentration is increased to 10 percent, a similar agitation causes voluminous flocs to form immediately. Although such flocs tend to sediment out, they often form a very fine suspended flocs and sometimes a thin layer of floating flocs. In general, when the agitation of a slurry of the sand and water is sufficient to release a substantial amount of oil from the sand, it tends to disperse enough clay to floc out the so-released oil.

It was found that, in view of the properties and behavior of the sands and clays in a produced fluid containing oily sand, the oil recovery procedure most readily adaptable for offshore marsh, or coastal conditions should feature a short, violent agitation of a mixtureof the oily sand and water followed by an immediate separation of the de-oiled sand to leave an oily water from which the oil could be removed in a flotation cell. And, such an agitation and separation can advantageously be accomplished by means of Venturi jets that can both entrain the sand being agitated and operate a cyclone centrifugal means for separating the sotreated sand. Once the sand has been de-oiled and separated from the water, the so-released oil in the remaining oily water can readily be removed, for example, by means of flotation and/or other types of oil-waterseparators.

Tests were made of three methods for providing a short vigorous agitation of an oily sand and water. The

sand used was a sample of oily sand obtained by treating a produced fluid containing water, hydrocarbons and oily sand, where the treatment was simply removing the hydrocarbons while leaving water and sand, then removing the sand by means of desanders or desilters while leaving the water. The sand used (except where otherwise indicated) came from tank bottoms and had been exposed to air and some evaporation or oxidation of the adsorbed oil had occurred. Analysis (by pyrolysis flame ionization detection) indicated 30,000 parts per million of adsorbed hydrocarbons on the sand with 3,200 parts per million being volatile at temperatures above about 350C. Over percent of the sand was smalher than 40 rn esh and larger than 300 mesh and the sand was composed of mostly q iiartz that contained a considerable number of hard black shale fragments, occasional lumps of soft clay and a few shale fragments. The brine used in most tests contained 7.3 grams per hundred cc sodium chloride 0.5 grams per hundred cc calcium chloride and smaller amounts of magnesium chloride and sodium bicarbonate.

The tested methods of agitating the sand and brine were (1) mechanical mixers such as a Hamilton Beach or Waring Blender, (2) intense ultrasonic radiation provided by a Blackstone Ultrasonic Probe Model BP-Z driven by an ultrasonic generator model SS-2A, which provided agitation enough to cause cavitation, and (3) a jet-cyclone arrangement of a Venturi jet and a cyclone desander of the type shown in the drawing. In the jet-cyclone arrangement, the jet functions to provide both high shear mixing, in the Venturi tube, and an operation of the cyclone. The jet-cyclone operates in a manner such that the abrasive slurry does not pass through the pump or the jet nozzle.

The efficiency of the three types of agitating procedures were compared by measuring the amount of power consumed per pound of sand deoiled to a given level. The measurement data is contained in Table 1.

In the cyclone bowl.

In each stage, the mixture of oily sand and water was agitated for the indicated number of minutes, with the sand then being allowed to settle out, for an oil content determination by pyrolysis flame ionization detection or the sandy water being subjected to the next state of agitation. The results indicated that the jet cyclone is the most efficient, probably because the oil is so quickly removed after being released from the sand grains.

the trade name BUTYL OXlTOL and BUTYL DIOX- ITOL.

What is claimed is:

TABLE 2.-REMOVAL OF OIL IN LABORATORY JET-CYCLONE Surfactant vcnturi Jet Water Conesaud Cqncsand n 1ia. jet output, pressure, in hopper, 111 cone, thruput, Gone. in core No. of carbons tube, in. g.p.m. p.s.1. 2.]100 cc. gJlOO ec. lb./m1n. Brand name stages added stazcs p.p.111l

Sample of Sand from Dump 55 -15 2,2 B 120 1.8 0.4 Herder 6 2 400 1 52 2.21; 120 10 1.8 0.1 do 10 1700 m m 2.5 B 120 10 4.5 1.5 t1o. 5 2'000 32'12-912 2.3 1 120 3 1.11 5 2'000 11-952 3.81" 120 a .75 .31 Nude. 11 1' 500 -9112 4.0 F 120 o 1.45 .63 5 1400 ,5- .5 4.15 120 10 2.2 1.0 s 1'100 M1 152 5.01 200 10 2.5 1.35 5 990 r 3 5,01 200 6 1.5 .7 6 1,000 144 5 5,011 200 6 1-5 6 55-952 5.011 200 6 1.5 .78 s 35-952 5.013 200 s 1.5 .78 s 93 3 5,013 200 6 1.5 .7 6

Sample of Sand from Desauder Discharge Ax-9&2 5.011 200 6 1- 1 4 151-952 5.0 B 200 o 1.5 2 5 lit-e52 5.0 B 200 5 1.5 3 10 P952 5,011 200 5 1.5 4 10 nt-952 5.0 B 200 10 2.4 1 2o B=syntl1ctie produced brine, F=frosl1 water. percent from 3rd to last stage.

The data in Table 2 indicate that the amount of residual sand grain adsorbed hydrocarbons decreased with: (I) an increase in the number of stages, (Experiments l and 2); (2) an increase in jet size (Experiments 4 and 5); (3) an increase in jet pressure (Experiments 7 and 8); and (4) an increase in sand concentration (Experiments 5, 6 and 7).

Note that with the sand from the cyclone desander discharge, which was very much cleaner than the previous sample from the dump (Experiments l4-l8), the residual hydrocarbons on the sand grains (after they had been separated from the associated water and rinsed lightly) were only 340 parts per million and there were 600 parts per million in the associated water. These experiments show that there were only 10 parts per million of oil adsorbed on the sand after three passes through the jet-cyclone arrangement. The total power consumed by the three stages was only 0.05 KWH per pound of sand. There was no sand in the overflow from the cyclone even when the concentration of the sand in input slurry was 10 percent by weight of the water. Very little clay was observed in this sample and only traces of floc developed in' theoily water cyclone overflow. In the treatment of this sand, the addition of an oily liquid surface tension increasing surfactant such as the oil herder made no significant difference.

The preferred composition of an oil-phase liquid, in- 1 terfacial tension increasing surfactant for use in the present invention comprises a non-toxic blend of a primary essentially straight long chain aliphatic alcohol having some branching of less than 5 percent of the formula ROH where R is preferably a straight chain alkyl or alkenyl radical of some 10 to 20, and preferably 12 to 15, carbon atoms, said alcohol being dispersed in a polar aliphatic solvent containing at least one hydroxyl, ether, ester, ketone, keto-alcohol, keto-ether, ketoester or ether-alcohol group in the molecule, said aliphatic alcohol being dispersable in a concentration of from about 10 to percent, or greater, in the solvent. Suitable long chain alcohols are available from Shell Chemical Company under the trade name of NEO- DOL, such as NEODOL 23, 25 or 45. Preferred solvent mono or dibutyl ethers of ethelene glycol, commercially available from Shell Chemical Company under l. A well operating process for treating a mixture of water, unadsorbed hydrocarbons and oily sand to isolate the hydrocarbons, a substantially oil-free water and a substantially oil-free sand, comprising:

removing said unadsorbed hydrocarbons while leaving a water suspension of oily sand; partially de-oiling the sand in said water suspendion by entraining the suspension in the stream of a relatively high speed jet of water; centrifugally removing a water suspension of partially deoiled sand from said water stream while leaving an oily water; further de-oiling said partially de-oiled sand by entraining a water suspension of it in at least I additional stream of a relatively high speed jet of water; centrifugally removing a water suspension of substantially oil-free sand from at least one of said additional water streams while leaving an oily water; and removing oil from said oily water while leaving a substantially oil-free water.

2. The process of claim 1 in which the centrifugal separations of said suspensions of sand in water streams are effectedby flowing the streams in circular paths in which sand-separating centrifugal forces are generated by the rapid swirling motions of the streams substantially immediately after the sand has been entrained in the streams.

3. The process of claim 2 in which said removing of oil from oily water is effected by flotation.

4. The process of claim 1 in which a plurality of wells are operated by treating a mixture of their produced fluids.

5. The process of claim 1 in which at least a portion of the oil-free water left by said separation of oil is used to form at least one of said relatively high speed jets of water.

6. The process of claim 1 in which a surfactant material 'adapted to increase the surface tension of an oilphase liquid is mixed with the water suspension of oily sand left by said removal of hydrocarbons.

7. The process of claim 6 in which said surfactant material is a polar-group-containing aliphatic solvent solution of a relatively long chain aliphatic alcohol. 

2. The process of claim 1 in which the centrifugal separations of said suspensions of sand in water streams are effected by flowing the streams in circular paths in which sand-separating centrifugal forces are generated by the rapid swirling motions of the streams substantially immediately after the sand has been entrained in the streams.
 3. The process of claim 2 in which said removing of oil from oily water is effected by flotation.
 4. The process of claim 1 in which a plurality of wells are operated by treating a mixture of their produced fluids.
 5. The process of claim 1 in which at least a portion of the oil-free water left by said separation of oil is used to form at least one of said relatively high speed jets of water.
 6. The process of claim 1 in which a surfactant material adapted to increase the surface tension of an oil-phase liquid is mixed with the water suspension of oily sand left by said removal of hydrocarbons.
 7. The process of claim 6 in which said surfactant material is a polar-group-containing aliphatic solvent solution of a relatively long chain aliphatic alcohol. 